The term 'up to a time' can be expressed as 'UNTIL' in five letters. This phrase is used to indicate that something will happen or continue UNTIL a certain point in time. For example, one might say 'I will work on this project up to a time' to indicate that they will work on the project UNTIL a certain point in time. It is also used to indicate that something will not happen beyond a certain point in time, such as 'I will not accept any more applications up to a time'.